Flash lamp



Feb. 22, 1 944. D; E. ELMENDORF FLASH LAMP Filed March 22, 1941 His AHorhe L Inventor v Dur' ea E. Elmendor'f,

Patented Feb. 22, 1944' Duryea E. Elmendorf,

to General Electric Company,

New York Cleveland, Ohio, assignor a corporation of Application March 22, 1941', Serial No. 384,622

11 Claims.

My invention relates to flash lamps and more articularly to that type of flash lamp used for photographic purposes which comprises a bulb containing a readily combustible light-giving material which, when ignited, produces a momentary flash of actinic light of high intensity. The present application is a continuation-in-part of my co-pending application Serial No. 371,318, filed December 23, 1940.

In flash lamps in general use at present, the combustible light-producing material usually consists of a quantity of metal foil or filamentary material loosely arranged within the active por tion of the bulb. To initiate the actinic reaction in such lamps, suitable ignition means is provided therefore which usually comprises a resistance element or filament embedded in a bead of ignition paste and supported Within the bulb in close proximity to the loosely arranged combustible metal filling by a conventional mount structure. The ignition paste used is extremely sensitive and when the electrical circuit through the filament is energized, the heated filament promptly ignites the bead of ignition paste which, in turn, ignites the combustible material, thus initiating the actinic reaction.

Of recent date, a new type of flash lamp has been introduced in which the light-producing material consists solely of one or more beads or coat-' ings of a readily ignitable light-producing material as the sole source of actinic light, the beads or coatings preferably being disposed on the inner leads and ignition filament of the lamp mount structure. Such a flash lamp is shown in pending application Serial No. 328,399-M. Pipkin, filed April 8, 1940, now Patent No. 2,291,983, dated October 4, 1942.

As a safeguard against-explosion of the glass bulb when flash lamps of either of the above types are flashed, it is common practice, in the manufacture of such flash lamps, to test the completed lamp for the presence of air. One wellknown method of conducting such a test, known as a coil or glow test, consists in the use of high frequency equipment, the lamp base being connected to the high potential end of the high frequency generator and the lamp bulb being placed closely adjacent an external electrode at ground. potential. Such a method of testing, however, results in the loss of a considerable number of flash lamps through the premature flashing of the same, termed flash outs, which premature flashing iscaused by the occurrence of an arc discharge between the loosely arranged combustible metal fllling and the ignition filament structure, or by the occurrence of a glow discharge at the portion of the leading-in wires where the bead or coating of combustible light-giving material is located. Furthermore, spontaneous flashing of such lamps is apt to occur, during handling and transportation of the same, by the development of a static charge within the combustible metal fllling, the static charge building up to the point where it discharges to the filament structure, the

resulting discharge igniting the lamp.

One object of my invention is to provide an improved flash lamp which will not flash prematurely when subjected to various external phenomena, such as high frequency, corona, or the like.

Another object of my invention is to provide a flash lamp which will not flash spontaneously by the development of a static charge in the looselyarranged' combustible metal filling of the lamp where such a fllling is used.

Still another object of my invention is to provide a flash lamp having an auxiliary or antenna wire within the bulb for the purpose of picking up or collecting the glow discharge which occurs within the lamp during the glow testing thereof.

A feature of the invention is the provision of an extension on one of the leading-in wires of the ignition filament structure, which extension projects well into the active portion of the bulb and which, in the case of flash lamps employing a loosely arranged combustible metal filling, positively contacts such filling and grounds the same to the filament structure.

Further objects and advantages of my invention will appear from the following disclosure 01 species thereof and from the accompanying drawing in which'Fig. 1 is an elevation of one form of flash lamp comprising my invention; Fig. 2 is an elevation of another form of flash lamp according to the invention; and Fig. 3 is a. diagrammatlc illustration of one arrangement for testing flash lamps according to the invention for the presence of air therein.

Referring to the drawings, Fig. 1 illustrates the invention in connection wtih a-flash lamp of the type in which the combustible light-giving material is in the form of a loosely arranged mass of metal foil, or filamentary wire or rib bon. Referring to Fig. 1, the flash lamp there shown comprises a sealed light-transmitting bulb or envelope ill of suitable material, such as glass, having a bulbous or active portion II and a neck I: provided with a reentrant stem IS. The bulb I0 is filled with a combustion supporting gaseous filling, preferably oxygen, and com mount structure.

disclosed and claimed in co-pending applicaation.

Serial No. 269,197-H. D. Blake, filed April 21, 1939. Mounted within the bulb l0, Within effective ignition range of the combustible material it, is a small filament the ends of which are connected to leading-in wires I6, I 8 which are sealed into the press portion ll of the stem l3 and extend through the latter to the terminals of a conventional lamp base 18.

In the insertion of the filament mount into the bulb, the filament carries the metal filling I! along with it up into the bulb. As a result, the filament is located more or less within the lower region of the mass of combustible filling material so that the leading-in wires l6, 18 are normally out of effective contact with the filling material. The filament l5 and adjacent portions of the leading-in wires I8, I 8 are coated with a layer of a suitable fulminating substance I9 to thereby form the primer or ignition means for the lamp. The fulminating material is preferably of the type disclosed and claimed in copending U. S. application Serial No. 278,288, filed June 9, 1939 by George H. Meridith and assigned to the assignee of the present application.

In accordance with the invention, one of the leading-in wires 68 is provided with a metal extension or conductor which projects well into the space within the active portion of the bulb so as to extend through and contact a considerable portion of the metal filling M disposed therein and thereby insure positive grounding of such filling to the leading-in wires or filament The extension or electrode 20 is preferably in the form of a wire of suitable size bent into the shape of an L and welded or otherwise secured to the leading-in wire l6 at a point intermediate the vstem press Fly and the filament H5. The Wire 20 is preferably secured to the leading-in wire iGso that its longer leg 2| extends in a direction generally parallel to the axis of the bulb to a point some distance beyond or above the filament l5. 9

Instead of forming the grounding wire or extension 20 as a separate member suitably fastened to the leading-in wire I8, it may be formed as an integral extension of one of the leading-in wires l6, l6. Such a construction, however, does not lend itself as well to automatic manufacture of the filament mount.

Because of the positive contact of the wire extension 20 with the combustible metal filling l4,

any electrical charge, which is developed in the metal filling is effectively transferred therefrom through the conducting extension 20 to the lead- .ing-in wire l6. As a consequence, no discharge between the metal filling and the filament mount structure, and therefore no premature flashing of the lamp, will result.

In addition to its function as a grounding member for the metal filling ll, the wire extension 20 also serves as an additional support means therefor, the wire tending to minimize the displacement'or shifting of the metal filling within the lamp bulb during transportation and flash lamps slower but sometimes very dlfllcult I to make them faster.

Fig. 2 illustrates the invention applied to a flash lamp of the type disclosed and claimed in the aforesaid Patent No. 2,291,983 of M. Pipkin, in which the combustible material consists solely of a bead or coating of a readily combustible light-producing substance on the inner leads and ignition filament of the lamp. I have found that when such type flash lamps are subjected to the conventional glow test which is used to detect air leakage into the bulb, a glow discharge occurs at the tips of the inner leads and instantaneously sets 03 the readily ignitable combustible material thereat. As a result, I have found it to be essential, in such type flash lamps,

to provide an auxiliary or antenna wire within the bulb, such as shown and described in connection with Fig. 1, in order to pick up the glow discharge and so prevent accidental flashing of the lamp during the glow testing thereof. At least, no other way is known at present to those skilled in the art for preventing such accidental flashing of the lamp during the glow testing thereof.

Referring to Fig. 2, the flash lamp there shown comprises an ovoidal shaped bulb or envelope 22 having a relatively short neck portion 23 entirely enclosed and reinforced by a base 24 secured thereto. The bulb 22 is filled with a combustiomsupporting gaseous filling, preferably oxygen, at a suitable pressure, for instance from 100 mm. of mercury up to one atmosphere or so, and is provided with a protective lacquer or varnish coating the same as described above in connection with Fig. 1. Sealed into the bulb 22 is a small mount structure similar to that shown in Fig. 1 comprising a reentrant stem 25 having a pair of leading-in wires 26, 26 sealed into the I press portion 21 of the stem 25 and extending 30 such asdisclosed in the aforesaid patent No.

2,291,983 of M. Pipkin, the said substance constituting the sole source of actinic light. The light-giving substance 30 preferably consists of amixture of magnesium and zirconium metal powders, potassium perchlorate powder and sodium chlorate powder bonded together by a suitable binder such as nitrocellulose.

In accordance with the invention, one of the leading-in wires 28 is provided with a metal or wire extension or conductor 3|, similar to the conductor 20 shown in Fig. 1. As shown, the said wire 3| 'is secured to the leading-in wire 26 at a point intermediate the stem press 21 and the ignition filament 29 and considerably removed from the latter. The wire 3| preferably extends in the general direction of the bulb axis, in spaced relation to the inner leads 28, 28, to a point considerably beyond the ignition filament 2 9, and may have its upper end or tip portion 32 slightly bent toward the bulb axis so as to more or less overlie the ignition filament 29. However, the metal conductor 3| may be of any other suitable shape or form just so long as its free end or tip is spaced an appreciable distance from the ignition filament 29. Thus, the conductor 3| for instance, may consist instead of a short length of wire extending substantially straight out from the leading-in wire IE to which it is connected, i. e., in a direction at right angles, or nearly so, to the bulb axis. 7

By the use of such a wire extension 3 l the glow discharge which occurs within the lamp during the glow testing thereof and which would ordinarily take place at the tips of the inner leads 28, 28 where it would quickly set. off the fulminating substance 30 thereat, forms instead at and about the free end or tip 33 of the wire extension 3|. the said wire acting as an antenna in this respect to pick up the glow discharge. In this manner, the glow discharge is removed a sufficient distance from the fulminating substance 30 to prevent ignition of the latter.

Inasmuch as the glow discharge takes place more easily from a pointed electrode, the tip or free end 33 of the wire extension 3| is preferably pointed, such as by cutting the same at an angle, or by forming the extension 3| of fine wire so that the free end thereof approximates a point. In this way, the formation of the glow discharge at the tip 33 of the wire extension 3| is facilitated.

As in the previous modification, the antenna or electrode wire 3|, instead of being formed as a separate member suitably fastened to the leading-in wire 28, may be formed as an integral ex tension of one of the leading-in wires 28, 28.

Fig. 3 illustrates one arrangement for testing flash lamps for the leakage of air thereinto by the formation of a high frequency glow discharge therein. As shown, the apparatus comprises a downwardly inclined slip socket 34 adapted to receive the base of the lamp to be tested and contact both terminals thereof so as to short circuit the same, the said socket being electrically connected by lead 35 to one end of a Tesla coil 36. A metal cup 31, preferably of brass and filled with water, mercury or other suitable conducting liquid 38, is so arranged with respect to the slip socket 34 as to submerge in the conducting liquid 38 a small portion of the bulb 22 of the lamp to be tested when the latter is in place within the slip socket 34. The said cup 31, with its filling of conductive liquid 38, constitutes the external electrode of the testing apparatus and is con nected to ground by lead 39. The end of the Tesla coil 36 opposite to that end connected to the slip socket 34 may be connected to the metal cup 31 and/ or ground by lead 40 as shown, or the grounding may be taken care of by the inherent capacitance to ground of the" high frequency generator 4|. The low potential end of the Tesla coil 36 is inductively coupled 'to a source of high frequency 4| by means of an inductance 42 in the manner well-known to those skilled in the art.

The flash lamp to be tested is inserted in the slip socket 34 and properly positioned therein so that a small portion of the surface of the bulb 22, adjacent the tip thereof, is submerged within the conducting liquid 38 in the cup 31. The bulb is further positioned so that the free end or tip 33 of the metal conductor 3| is located closer to the external electrode 38 (i. e., the conducting liquid within the cup 31), than is the bead of fulminating substance 30. This condition is always present with the arrangement shown in the drawing regardless of the rotative position of the lamp in the slip socket 34 due to the location of the tip 33 of the metal conductor 3| intermediate the bead of fulminating substance 30 and that portion of the bulb (i. e., the tip portion) which is in contact with the external electrode 38. With the flash lamp positioned in the test apparatus in the above indicated manner, the electrical circuit through the lamp is energized by the high frequency source 4|, whereupon a glow discharge occurs within the lamp bulb 22 at and about the tip 33 of the metal conductor 3|, the glow discharge thus being confined to a location within the bulb remote from the bead of fulminating substance 30. By observing the color of the glow discharge, the presence or absence ofnitrogen within the bulb can be readily determined, a bluish-white colored glow indicating relatively pure oxygen or a good lamp while a pink or purple colored glow indicates the presence of nitrogen due to the leakage of air into the bulb.

What I claim as new and desire to secure by Letters Patent of the United States is:

l. A flash lamp comprising-a'sealed transparent container, a quantity of fulminating substance within said container, contact means at the exterior of said container, and a metal conductor within said container electrically connected at one end to said contact means and, in a normally operative lamp, having a free end portion extending to and terminating at a point within said container remote from said fulminating substance so that a high frequency current applied to said contact is discharged through said conductor and out of said container at a point sunlciently remote from said fulminating substance to avoid ignition 'of said substance.

2. A flash lamp comprising a sealed transparent container, a pair of leading-in wires extending into said container, a filament disposed within said container and electrically connected to said leading-in wires and forming therewith a continuous conductive path within said container, a quantity of fulminating material disposed adjacent to and coated on at least a portion of said filament, and a wire electrically connected to one of said leading-in wires and having a free end portion extending upwardly in the general direotion of the container axis and terminating at a point above and appreciably spaced from said fulminating material.

3. The method of testing flash lamps, of the type comprising a sealed transparent bulb containing a bead of fulminating substance therein and having within, said bulb a metal conductor electrically connected to an external contact of the lamp and extending to and terminating in a free end portion at a point within the bulb remote from said bead of fulminating substance, which method comprises positioning an external electrode closely adjacent the bulb of the lamp in a position nearer to the free end of the said metal conductor within the bulb than to the said bead of fulminating substance therein, and connecting said external electrode and said external lamp contact to a source of high frequency current to thereby form a high frequency discharge within said bulb at a point remote from the said bead of fulminating substance therein.

4. A flash lamp comprising a sealed transpara fulmlnating substance and a filament disposed within said container ior igniting said combustihis material, said means including leading-in wires normally out effective contact with said combustible material and arranged to carry current to said filament, and a conductive extension on one of said leading-in wires extending into effective contact with said combustible material, the said. extension terminating at a point within said bulb an appreciable distance away from said lulminating substance.

5. A flash lamp comprising a sealed transparestates ing loosely arranged within said container, igniill ent container, a readily combustible metallic fllling loosely arranged within said container, means comprising a iulminating substance disposed within said container for igniting said metallic filling, said means including leading-in wires normally out of effective contact with said metallic filling, and a conductive extension electrically connected to one of said leading-in wires and extending well into the mass of said metallic filling to thereby eifectlvely contact and ground said filling to said leading-in wire, the said extension terminating at a point within said bulb an appreciable distance away from said fulminating substance.

6. A flash lamp comprising a sealed transparent container, a readily combustible metallic filling loosely arranged within the upper portion of said container, means comprising a fulminating substance disposed within said container at the lower region of the mass of said metallic filling for igniting the latter, said means including leading-in wires arranged within the lower portion of said container and normally out of effectice contact with said metallic filling, and an upwardly extending conductor on one of said leading-in wires extending well up into the mass of said metallic filling to thereby effectively contact and ground said filling to saidleading-in wire, the said conductor terminating at a point within said bulb an appreciable distance away from said fulminating substance.

7. A flash lamp comprising a sealed transparent container, a readily combustible metallic filling loosely arranged within said container, ignition means for said metallic'filling comprising a tion means for said metallic filling comprising a filament and associated fulmlnating substance arranged within the lower region of the mass of said metallic filling and leading-in wires electrically connected to said filament and normally out of eflectlve contact with said metallic filling, one or said wires having an integral extension projecting well into the said mass of metallic filling to thereby efiectively contact and ground said filling, the said extension terminating at a point within said bulb an appreciable distance away from said fulminating substance.

9. In the manufacture of flash lamps, of the type comprising a sealed transparent bulb containing a quantity of fulminating substance, the steps which comprise providing electrode means within said bulb at a point remote from said fulminating substance and then testing for leakage of air into the bulb by applying high frequency current to the electrode means to form a glow discharge at ,a point within said bulb sufficiently remote from said fulminating substance to avoid ignition of said substance.

10. In a flash lamp comprising a sealed transparent container, 9. quantity of fulminating material in said container, electrical ignition means {or igniting said fulminating material, means to carry current to said ignition means from the exterior of the container, and electrode means in said container electrically connected to a contact at the exterior of said container and terminating in a free end portion located at a point remote from said fulminating material so that a high frequency current introduced into said electrode means is carried thereby to its free end portion to form thereat a glow discharge which will indicate the presence or absence of air in the container without igniting the fulminating material.

11. In a fiash lamp comprising a sealed transparent container, 9. pair of lead-in conductors extending into said container from the exterior thereof, a filament bridging said conductors and forming therewith a continuous conductive path within the container, a quantity of fulminating material associated with said filament so as to be ignited thereby, and electrode means comprising a conductor electrically connected to one of said lead-in conductors and terminating in a free end portion located at a point within said container remote from said tulminating material so that a high frequency current applied to said one of said lead-in conductors is carried by,sald elec trode means to its said free end portion to form thereat a glow discharge which will indicate the presence or absence of air inthe container without igniting the fulminating material.

DURYEA E. ELMENDORF 

